Superheater element for flue-tube boilers.



THMSEN, GE. AESEL, GERMLNY, SSIGNJZ. "EO SCHMIDTSCHE HEISSAMPF iirifitidbi GESELLSCHAFT NL B. H., #DF CASSELJHLHELMSHHE, GERMNY, A CBIPGRTIN OF G-Eltfifi NY.

SUPERHEATER ELEMENT FOR F11UE-TUBE BOILERS.

Specification 01E Letters atent, Pmygmm! DQ@ 1125 pgp@ applieation fried Goteborg, i915. Serial No. 553,555.

lue tube boilers which suitable loopedpipes or superheater elements are inserted in some or ali oi the iiue tubes; steam flows ing from the boiier to the engine, through these pipes, is superheated by the hot gases passing through the iue, tubese p More partieulariy my invention relates to the use ot a plurality ot parallel connected loops in a single due tube. Elements so constructed. aii'ord a large cross section for the passage of steam, buthave the disadvantage that the superheated ends of the elements adord a large surface of Contact to tbe flue gases passing from the end of the flue tube into the lsmoke box which lue gases have already largely lost their heat to 'the super-l heater pipes; as a consequence there 1s an actual 'heat transfer from the superheated element ends to these iiue gases, the magnitude of the same being dependent upon the temperature difference.

According to the present invention the above mentioned disadvantage avoided, without diminishing the' necessary and advantageous cross section of the pipes, by causing the several parallel connected tube ioops to be united on the superheated steam side, to a common enit pipe having a cross section equal to the sum ot the cross sections oi' the individual pipes. By choosing; a suit* able location for the joint between the individual. ends and the exit pipe, inside of the flue tube, there also results the possibility of making the supcrheating of the steam independent of the iinal temperature ot the this gases, Within practical limits at any rate, since the heat transfer will become quite small byreason of the lesseniug of the surfaces involved which is thus brought about. in order, further, to lessen the number of connections between the elements and the steam collectors` or headers, as also to make the number of such connections for superheated and wet stef'ln ends equal, I may also join the saturated steam ends oi? the paraileled elements to a common coileetiug or inlet pipe having a section equal to the sum of the individual pipes.

My invention willbe better understood byv referring to the accompanying drawings in which- Figure i. shows diagrammatically, a pair ot parallel connected superheater elements, according; to the known art, in a single flue tube each element comprising two individual parallel pipes; Figs. 2 and 3 show, also diagrammatically, super-heater elements according to my invention .in two dii'lerent embodiments; Fig, is a, vertical longitudif nal section through a flue tube containing an element constructed according to the diagram of Fig. 3; Fig. 5 4is a front viewoiE Figa 4; Fig. G is a cross section through Fig.

4i etong lthe line ti-6g Fier. is a similar cross section along the lines 7 7 of Fig. 4; and Fig. 8 is a vertical longitudinal section through a iiuev tube containing another e1n bodiment of my invention.

In the known arrangement, shown in Fie. 1, there are` two parallel U-sha'ped pipe loops o and in the fine tube o so that the steam to be superheated flows into the stream oi' flue gases `und then back again; as the steam enters the flue tube its direc tion of flow is contrary to that of the flue gases and as it leaves the Hue tube its direc* tion is the saine as'the flue gases. in the irst, or saturated, portion of the element the amount of heat absorbed is very great, because the temperature di (Terence between the outgoing flue gas and the incoming wet steam is itself great. 0n the other hand in the last, or superheated, part oi the element there is no longer any absorption of heat by the steam but, on the contrary, it may even happen that the superheated steam will itself lose heat to the flue gases because said gases, at their exit into the smoke box, will have a temperature less than that of the superheated steam.y Upon the assumption that tle temperature of the flue gases at exit is about 300O C., that of the steam on the saturated steam side of the element about iO C., and that of the steam on the superheated steam side of the element about 850 C.

there will be, at about the center of the superheatedA steam part ofthe element, substantiaily no heat absorption silice the temperature diierence between the line gases and steain at 'this point 'will only be about 200 C. .fl-.t the exit end of the element there is not only a failure to further supeiheat the steam, but the superheated steam actually gives back a certain amount of heat to the flue 2f-ases. With a higher degree of superheat, say to about 400O C. this etl'ect becoii'ies even more important.

Elements made according to my present invention, as shown in F Zand 3, avoid the above disadvantages. cording to Fig. 2 comprises two parallel U-shaped loops d and e, each having` a re* turn bend g, with their superheated ends opening into a common exit pipe .f of cross section equal to the suin of the cross sections oit' the individual pipes d and e. The point at which pipe f joinstiie individual pipes Y and is placedwell within the flue tube c.

ln the form of my invention shown in Fig. 3 the saturated steam ends of the two loops and Il.' are also connected to a coinmon pipe m through which saturated steam enters the element-s. The junction point, n, between pipe lm and the saturated steam ends is locatedfat the sinolie box end of the due tube in order that the heat ot the outiowing flue gases may be employed upon large a heating surface as possible. .his junction point of the saturated steam ends with theinletpipe may, conveniently, be placed entirely outside of the iiue tube end in the smoke box in order that on this side where the steam temperature is relative y low, all the pipe lengths may be passed over by the hot gases as they ascend in the smoke bon. The superlieated steam sides of the indi-l vidual loops are shorter than the saturated steam sides so that the common exit tube o extends well into the flue tube; the actual distance to which the tube o extends in the iiue Atube may be varied according to the temperature of the gases flowing from the line tube. ln this way the superheated sur! tacos capable of giving off heat are made smaller. This forni of element affords the` further advantage that, in spite oi'f there being four loop lengths within the Hue tube each element has but two ends which must be united to the steam collectors.'

Since the superheated steam end of an ele,-

rnent, according to the invention, requires less space inside the flue tube than would be required by the ends 'otindf `id .ial loops leaving; the same cross section, t'h'e'spepe thus ined may be partially utilized by-iiisulation sirroundiiig the su perheated end, thus Vstill,itui'ther diminishing the eventual heat loss from the superheated steam end.

f An element such as has been described Amay be so constructed that each loop j and 7c is arranged in a horizontal plane in the smoke tube c, as shown in Figs. i to 7. ln this construction the two terminal pipes mv An element acand o, as they emerge from the smoke tube, are also arranged in a horizontal plane.

Fig. 8 shows another modification in.

which the two loops r and s' are in two par- .'plished either by welding or the equivalentl or through the use of special connecting pieces such as are shown, e g., in German Patent No. 274,603.4

Having described my invention, I claim: 1. In a boiler provided With flue tubes, a superheater element comprising a plurality of completely independent parallel U-shaped loops inserted in some ofthe flue tubes, the superheated ends of the loops being connected to a common exit pipe having a cross section substantially equal to the sum of the cross sections of the individual pipes.

f2. In a boiler provided with ilue tubes, a superheater element comprising a plurality of completely independent parallel U-shaped loopsinserted in some of the liuc tubes both `the superheated ends and the saturated ends of the loops being connected respectively to common exit and inlet pipes having cross sections substantially equal to the sum of the' cross sections of the individual pipes.

3. In combination with a boiler provided with liuc tubes and a smoke box,-a superheater element comprising a plurality of completely independent parallel U-shaped loops inserted in some of the flue tubes, both the superheated ends and the saturated ends of the loops being connected respectively to common exit and inlet pipes having cross sections substantially equal to the suin of the cross sections of the individual pipes, the connecting point of the superheater ends being within a tine tube and of the saturated ends within the smoke box.

4. The combination, with a 'locomotive boiler iue, of two parallel ,Ueshaped steam superheatiiigtubes arranged within said liuc and consisting` each of a long leg and of a shortleg, neans to conduct saturated steam simultaneously into the iends of the two long legs, a connection; between the ends oi' the two short legs, and a lthird tube connected with said connection and adapted to lead I oit the steam super-heated. within said two lil-shaped tubes.

5. |The combination, withv a Vlocomotive boiler AVlue, of two :parallel @shaped :steam super-heating tubes 'arranged within said tx'eoeeet Y e Hue and consisting each of along leg ett ythe steam ,superheated Within seid two of e, short 1egaconnection between the ends of the two long legs; means to conduct saturated steam into said connection, e' connection between the ends of the two short legs, endl e third tube connected with said second connection :md adapted to leed oft U-shaped tubes.

:PETER THOMSEN.

l Witnesses:

JEAN GRUND, CARL GRUND. 

